The long-term objective of this project is to develop cell lines that stably express G-protein coupled CNS receptors important to mental health. The specific aim of this application is to demonstrate the feasibility of the project by developing a permanent cell line expressing the human D1 dopamine receptor (d1R). Cell lines which express CNS receptors will be useful in functional assays for finding new ligands (drugs) which will be highly specific for receptor subtypes and thus be effective therapeutic agents with minimal side effects. The methodology for achieving these goals involves a powerful functional assay system in which melanophores from Xenopus laevis disperse or aggregate their pigment granules upon appropriate ligand-receptor interaction. Transient expression of the cDNA for a human D1R results in pigment dispersion which is easily detected visually. Expression of this cDNA in conjunction with a selectable antibiotic resistance marker will allow for establishment of a permanent cell line expressing the D1R. This research will represent a breakthrough in technology for functional screening of ligands for this receptor. Drug development will be the commercial application. PROPOSED COMMERCIAL APPLICATION: Functional assays for ligands which interact with G-protein coupled receptors are limited in availability and usefulness. This research solves these limitations and provides a new and useful tool with which to find new drugs to these receptors. The large number of such receptors in the CNS, large number of disorders linked to these receptors and success in licensing the technology suggests wide commercial applicability of this research.